Raw whey is the liquid by-product resulting from traditional cheese making and casein manufacturing including acid whey, sweet whey, salt whey, permeates from the production of whey protein or milk protein concentrates and lactose etc., motherliquor from lactose crystallization, demineralised whey and similar products.
In the present context the term whey will be used for liquid raw whey which may have been subjected to various pre-treatments whose purpose is to improve the bacteriological quality, remove possible cheese fines and to reduce a possible content of fat and salts.
Depending on origin the whey contains 5.5-6.5% total solids, wherein 0.7-0.9% protein, 0.05% fat, 4.2-4.6% lactose and 0.5-0.8% ash.
Usually, after a number of pre-treatments, the aqueous whey is a solution in which the lactose is in an equilibrium of 60% beta- and 40% alpha molecular form. This mixture is hygroscopic and unsuitable for creating a free flowing, non-caking powder.
However, a suitable powder can be obtained when a major part of the lactose is converted to the alpha monohydrate form, which is done by crystallization.